The present invention relates to pharmaceutical compositions useful for treating psoriasis and, more particularly, to a cruciferous plant extract and/or isothiocyanates which are capable of treating psoriasis lesions.
Psoriasis is a common, non-contagious, chronic skin disease affecting 2-4% of the Caucasian population. The main characteristics of the disease include the appearance of thick red zones of the skin covered by silvery or whitish scaled eruptions and plaques of various sizes and which exhibit variable degrees of pruritus. The extent of the disease is variable, with small local areas or the whole surface of the body being affected. The disease may also affect the joints, nails and the mucous membranes. The precise cause of psoriasis is still unclear. While traumatized areas may often develop lesions of psoriasis, some external factors such as infections, stress, and medications (e.g. lithium, beta blockers, and anti-malarias) may exacerbate psoriasis. Scaling occurs when cells in the outer layer of skin (cutaneous cells) reproduce faster than normal and pile up on the skin's surface. Such high production of cutaneous cells is probably mediated by the immunological system.
The most common variety of psoriasis is called plaque type. Patients with plaque-type psoriasis exhibit stable, slowly growing plaques, which remain unchanged for long periods of time. The most common areas for plaque psoriasis to occur are the elbows knees, gluteal cleft, and the scalp. Involvement tends to be symmetrical.
Eruptive psoriasis (guttate psoriasis) is most common in children and young adults and tends to appear following an upper respiratory tract infection with beta-hemolytic streptococci. Eruptive psoriasis is characterized by many small erythematous, scaling papules and may also involve pustular lesions which are either localized to the palms and soles or may be generalized and associated with fever, malaise, diarrhea, and arthralgias.
In about 50% of all psoriasis cases the disease involves punctate pitting, nail thickening or subungual hyperkeratosis of the fingernails. On the other hand, 5-10% of psoriasis cases suffer from a joint disease, including a single or a few small joints (in 70% of the cases), seronegative rheumatoid arthritis-like disease, distal interphalangeal joints, severe destructive arthritis with the development of “arthritis mutilans”, and a joint disease which is limited to the spine.
The treatment offered to psoriasis patients depends on the severity of the disease. While the less severe cases can be relieved using pomades or emollient creams which keep the skin hydrated, the more moderate cases of psoriasis are usually treated with topical formulations containing corticosteroids which are either applied underneath an occlusive covering made of cellophane or polyethylene, or incorporated into an adhesive bandage. However, depending on the affected area, applying such topical formulations represent a practical problem for the treated patients, especially during the day.
The more severe cases of psoriasis are treated by systemic therapies including methotrexate, cyclosporin A and retinoids. However, the use of such agents in the treatment of psoriasis is limited by severe side effects and the significant potential of nephrotoxicity, hypertension and liver toxicity.
There is thus a widely recognized need for, and it would be highly advantageous to have, methods and compositions for treating psoriasis devoid of the above limitations.